Such light grids are known from the prior art and serve, for example, to monitor areally extended monitored zones or protected fields for intrusions, for example by persons, and, on intrusion by a person, to generate a control signal which results, for example, in the switching off of a machine which has moving parts which could endanger the person intruding into the monitored zone. The use of a light grid is conceivable in the region of any kind of machines which can give rise to any kinds of danger.
A light grid is known from the German patent specification DE 44 22 497 C2 which does not generally result in a switching off of a machine when an object or a person intrudes into its monitored zone. This known light grid rather makes it possible to teach a fixed time sequence of permitted intrusions into the monitored zone of the light grid which then accordingly does not result in a switching off of the machine. It becomes possible in this manner, for example in the course of a bending procedure, for a workpiece to carry out a specific movement in which parts of the workpiece move through the monitored zone without a switching off of the machine taking place.
The fact is disadvantageous with this known light grid that only such permitted movements can be taught which run in a fixedly pre-determined time sequence.